[PIP2] Fix NPE crash when entering Maps

Adds null checks for entering Maps pip.

Flag: com.android.wm.shell.enable_pip2
Bug: 378124752
Test: manually enter maps pip
Change-Id: Ie746c80d14257ed50f1de16acb1a1796cc513bf8
diff --git a/libs/WindowManager/Shell/src/com/android/wm/shell/pip2/phone/PipTransition.java b/libs/WindowManager/Shell/src/com/android/wm/shell/pip2/phone/PipTransition.java
index 3caad09..f320f9e 100644
--- a/libs/WindowManager/Shell/src/com/android/wm/shell/pip2/phone/PipTransition.java
+++ b/libs/WindowManager/Shell/src/com/android/wm/shell/pip2/phone/PipTransition.java
@@ -420,7 +420,8 @@
         }
 
         // Update the src-rect-hint in params in place, to set up initial animator transform.
-        params.getSourceRectHint().set(adjustedSourceRectHint);
+        params.copyOnlySet(new PictureInPictureParams.Builder()
+                .setSourceRectHint(adjustedSourceRectHint).build());
 
         // Config-at-end transitions need to have their activities transformed before starting
         // the animation; this makes the buffer seem like it's been updated to final size.